A server-client system may be formed by a Web server and a client terminal that accesses a Web site provided by the Web server, via the Internet, for example. At the Web server, it may be useful to record a log of each access made to each Web page of the Web site from the client terminal. The Web beacon technology is an access analysis technique that has been proposed to record a log of when and who visited which Web page of the Web site provided by the Web server.
For example, the Web beacon technology embeds, with respect to each analyzing target Web page, a <img> tag in JavaScript that indicates an embedded image and causes a single-pixel image file for analysis to be read from the Web site. The <img> tag, that may be used in cross-domains, acts as a Web beacon. Information related to the visitors who visited the Web site may easily be analyzed by extracting the <img> tag element embedded in the Web page from the log of the access, and analyzing the log, which may involve counting or analyzing IP (Internet Protocol) addresses of the visitors included in the log. The single-pixel image file is used to avoid an unnecessary consumption of memory resources of the Web site and to avoid an unnecessary increase in the communication bandwidth, even if identical image files are embedded in different Web pages, for example.
But recently, a browser of the client terminal may have a caching function that uses cached data if a file has a file name or URL (Uniform Resource Locator) identical to that of the cached data. For this reason, a log of an access that uses the cached data and does not read data from the specified Web site will not be recorded.
Accordingly, a method has been proposed to nullify the caching function in order to always read the single-pixel image file from the specified Web site and positively record a log of the access made by a visitor (or user). According to this proposed method, a dynamically random parameter is added to a source of the <img> tag element, that is, to a file name of the single-pixel image file, in order to always intentionally cause an erroneous recognition of the single-pixel image file as being a new single-pixel image file and cause reading from the specified Web site. As a result, the log of the access is recorded each time the Web page of the specified Web site is accessed.
However, the Web beacon technology, even in combination with the proposed method, only records the log including information that enables an access statistic data to be obtained for each visited Web page of the specified Web site. An Apache HTTP (Hyper Text Transfer Protocol) server (Apache: Registered Trademark) has a function of recording a log of the access, including an IP address, a domain name, an access date and time (only in units of seconds or greater), an access page name, a referrer (that is, a page referred immediately prior to the access) and the like of the visitor. But even if the Web server is formed by the Apache HTTP server, for example, the log of the access only has a time resolution on the order of seconds. This time resolution on the order of seconds is relatively low when a human response speed, that is, a time required for a manual operation such as a mouse click to be made by the visitor at the client terminal, is taken into consideration. Furthermore, the log of the access is not recorded in an order of requests from the browser, but in an order of file transfer executions.
Consequently, the log recorded in the Web server does not store causality of operations associated with the access and made by the visitor, and does not necessarily accurately reflect the operations associated with the access made by the visitor.